Method and apparatus for rapid non-invasive determination of blood composition parameters

ABSTRACT

A method and apparatus for rapid non-invasive determination of blood composition parameters. A blood-containing body part of a live organism is irradiated with electromagnetic radiation of near-infrared wavelength range. Spectrum values of the radiation transmitted through and reflected by the body part are measured. One or more unknown values of blood composition parameters are determined on the basis of the measured values. The transmittance spectrum of the body part is measured at several wavelengths in a first wavelength range from 700 nm to a value between 1000 and 1100 nm. The reflectance and/or interactance spectrum of the body pat is measured at several wavelengths in a second range from the value between 1000 and 1100 nm to 1800 nm. The unknown values of blood composition parameters are determined on the basis of a single spectrum including spectrum values of said transmittance spectrum and spectrum values of said reflectance and/or interactive spectrum.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of the invention is a method and apparatus for rapidnon-invasive determination of blood composition parameters.

2. Discussion of the Background

In medical diagnostics it is often necessary to determine various bloodcomposition parameters, e.g. blood components like glucose, protein,albumin, creatinine, carbamide, cholesterol, triglyceride,cholinesterase, haemoglobin, etc. Measuring the glucose component isespecially important, because diabetes mellitus seems to be consideredas a widespread disease. For treatment of diabetes mellitus, glucosecontent of the blood must be regularly monitored. In line withup-to-date treatment principles, efforts must be made to close the gapas much as possible between the actual glucose component and thephysiological one. Therefore, frequent blood sugar measurement isindispensable. Even under hospital conditions it is a frequentoccurrence that only the determination of the glucose component isnecessary. Today some diabetics determine their blood sugar themselvesat home. This is primarily becoming a habit in areas having a developedhealth culture, but an objective should be to allow this opportunity forall patients.

There are widely used instruments which determine the glucose in bloodby photometry using a blood drop on paper strips saturated withreagents. However, this approach is far from being perfect, becausenumerous circumstances, like the age of the paper strips, thetemperature, the period elapsing between taking the blood sample anddripping it on the paper, make an unfavourable influence on the accuracyof measurement. But, the greatest concern is that the patient must bepricked in each case, because blood is required for the determination.Either the patient pricks himself or this is done by somebody else,sterility must be ensured. Even in the case of a patient reallyintending to cooperate, a very serious worry is the fact of beingpricked. For a young diabetes patient, the glucose in blood must becontrolled several times a day and this represents a lot of pricksthroughout his lifetime as diabetes cannot be cured at the moment.

Therefore, it would be a major benefit to be able to determine bloodcomponents and especially glucose content by a non-invasive technologyand, thereby, to eliminate the need of pricking the patient. The glucosecomponent could be determined more frequently than now, which wouldenable more accurate adjustment, and so complications of diabetes couldbe better avoided. Even patients difficult to cope with would be moreliable to measure the glucose in their blood themselves, because themeasurement would be absolutely painless. Furthermore, infection couldbe avoided with total security. Materials necessary for disinfectingwould not. be required neither reagents used so far for determiningblood sugar, and this would have high significance also from anenvironment protection aspect as people in many hundreds of millions areinvolved all over the world.

It is well known that the spectrum of electromagnetic radiationreflected by or transmitted through a material contains valuableinformation about the composition of the examined material. Forobtaining this information, numerous mathematical methods are available.Of these, worth mentioning are the "multiple linear regression" (MLR)method, which describes the correlation between spectrum values measuredat some characteristic wavelengths and a component to be determined, aswell as the "principal component regression" (PCR) and "partial leastsquares regression" (PLSR) methods which two latter methods describe thecorrelation between a component to be determined and so-called latentvariables, where each of the latent variables can be generated as afunction of all measured spectrum values in the form of a linearequation.

Organic materials, including body tissues, are most transparent in thenear-infrared (NIR) wavelength range. It has already been suggested touse NIR technology for non-invasive determination of glucose in blood.Such apparatus have been described, for example, in U.S. Pat. Nos.5,028,787, 5,777,476, 5,086,229, 5,237,178 and 5,362,966. Theseapparatus use NIR technology to measure glucose in blood in a part ofthe human body in transmission or interactance mode of operation, in awavelength range from 600 to 1100 nm, where the penetration ability ofelectromagnetic radiation is the highest. In this wavelength range, thesensitivity of silicon detectors is also satisfactory. The apparatusdescribed comprise infrared radiation sources, means for guiding theradiation to the examined part of the body, narrow-band filters,elements to position the body part in a measuring instrument, elementsto measure the thickness of the body part, elements to measure andprovide signal about the temperature of the body part and theenvironment, as well as detectors, amplifiers, signal processors anddisplay units serving for measuring the radiation exiting from the bodypart. In signal processing, it has been recommended to use first andsecond derivatives of the measured spectrum and also a normalisation. Asthe point of measurement, the distal phalanx directly behind the nail,the nose, the earlobe and the vein visible at the wrist and theelbow-joint have been proposed.

A transmission detection technique in the long wavelength infrared rangehas been suggested in U.S. Pat. No. 5,313,941 to monitor glucose andother blood constituents in a non-invasive manner. Short pulses ofrelatively high energy and narrow optical bandwidth are sent through afinger which pulses are synchronised with the heartbeat period. Theapparatus comprises a separate cardiac monitor which can be an opticalplethysmograph or an electrocardiogram.

A spectrophotometric method for non-invasive measurement of componentconcentrations in body parts has been described in EP-A1-0 636 876.Pulsed laser light of different wavelength are projected toward a bodypart and the light exiting from the body part is detected. Then, bycalculating an optimum lapse of time corresponding to an optimum pathlength, a quantity of the exiting light at the optimum lapse of time isdetermined. It has been suggested to utilize either transmitted light orreflected light or both, however, the description does not tell how toevaluate measurements if both transmitted and reflected lights aredetected and what wavelengths of light are to be used.

So far, however, there is no available apparatus using NIR technologyfor non-invasive determination of glucose in blood that could be appliedin a wide range of application with a sufficient accuracy.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and anapparatus for non-invasive determination of blood compositionparameters, especially of glucose content, with improved accuracy.

Studying the known solutions we have found that the reason ofinsufficient accuracy partly is that the known methods are using too fewspectrum values. For example, in the apparatus described in prior artdocuments referred to above, the spectrum is measured at somewavelengths, only and so disturbing effects of characteristicsinfluencing the measurement may not be eliminated. As a result, themeasurement may not be evaluated for certain persons. However, for anincrease of the number of spectrum values, it is to be taken intoconsideration that in the wavelength range of 700 to 1100 nm ensuring agood transparency of body tissues, the number of measurable spectrumvalues is limited due to a minimum bandwidth of monochromatic beams thatcan be generated. And, in the visible wavelength range below 700 nm,body tissues are less "transparent" and, furthermore, absorption peaksstemming from multiple overtones are of low amplitude and they areblurred because of overlapping. On the other hand, in the wavelengthrange of above 1100 nm, the sensitivity of silicon detectors dropssharply and the "transparency" also decreases, although the intensity ofabsorption peaks increases and they are better separated. Therefore, ifthe intention is to increase the number of spectrum values that is theinformation content, it must come partly from the range of longerwavelengths, but for this a different type of detector sensitive forthis wavelength range, for example an InGaAs or InGaAsP detector, isrequired and the transmission measuring method must be replaced byreflection and/or interactance measuring method. This is so because inthe wavelength range of 1100 to 1800 nm radiation can penetrate intobody tissues so deep that the information contained in the spectrum ofradiation reflected from the body surface does not only come from thesurface, i.e. the spectrum is partly of an interactance character.

Thus, on the one hand, the invention is a method for rapid non-invasivedetermination of blood composition parameters, comprising irradiating ablood-containing body part of a live organism with an electromagneticradiation of near-infrared wavelength range, measuring spectrum valuesof an electromagnetic radiation transmitted through and/or reflected bythe body part and determining one or more unknown values of bloodcomposition parameters on the basis of the measured spectrum values. Theinvention is characterised by measuring a transmittance spectrum of thebody part at several wavelengths in a first wavelength range from 700 nmto a wavelength value between 1000 nm to 1100 nm, measuring areflectance and/or interactance spectrum of the body part at severalwavelengths in a second wavelength range from said wavelength value to1800 nm, and determining said one or more unknown values of bloodcomposition parameters on the basis of a single spectrum comprisingspectrum values of said transmittance spectrum and spectrum values ofsaid reflectance and/or interactance spectrum.

In the method according to the invention, it is advantageous if both thetransmittance spectrum and the reflectance and/or interactance spectrumare measured at least at nine wavelengths. However, it is advisable tomeasure both spectra at a higher number of wavelengths, e.g. at 32wavelengths each, thereby increasing the accuracy of the determination.In the method according to the invention, the wavelength range of thetransmittance spectrum and that of the reflectance and/or interactancespectrum may join or be separated from or overlap each other. In thelatter case there are wavelength values at which both transmission andreflection/interactance are measured.

The measurement according to the invention can be carried out on anybody part which is sufficiently transparent for transmissionmeasurement. It is advantageous if both the transmittance spectrum andthe reflectance and/or interactance spectrum are measured on a finger ofthe examined person. Due to the fact that the measurements of the twospectra can be separated in wavelength and/or time, both measurementscan be carried out on the same phalanx of a finger, which is beneficialfor both the accuracy of the measurement and the design of theapparatus.

However, it is also possible that the transmittance spectrum is measuredon the distal phalanx of a finger of an examined person and thereflectance and/or interactance spectrum is measured on the middlephalanx of the same finger.

The measurement of the spectrum values in the transmittance spectrum andthe reflectance and/or interactance spectrum may be separated from eachother in time by measuring the spectrum values of the two spectraconsecutively in time. In some cases, the measuring rate can beincreased if the spectrum values of the transmittance spectrum and thespectrum values of the reflectance and/or interactance spectrum aremeasured at least partially alternately in time, i.e. after atransmission measurement a reflection and/or interactance measurementtakes place.

According to a further embodiment of the invention, the accuracy ofdetermination of blood composition parameters can be increased bymeasuring at least a part of the spectrum values of the transmittancespectrum and the reflectance and/or interactance spectrum with afrequency higher than the heartbeat period of the live organism,determining therefrom a characteristic changing in accordance with theheartbeat rhythm, and selecting the spectrum values for determination ofsaid one or more unknown values of blood composition parameterssynchronously with periodical changes of said characteristic.

At the point of spectrum measurement, e.g. in the fingertip, the volumeand thickness of the measured body part, and of course simultaneouslywith the change in volume the quantity of blood therein, changeperiodically according to the heartbeat period. So it is not irrelevantin which phase of this period the spectrum measurements are carried out,or which phase is used for selecting the spectrum values for thedetermination. One measurement, i.e. taking a complete spectrum,requires some milliseconds by currently available opto-electronicelements, which is much less than the period of 500 to 1000 ms of theheartbeat. According to the invention, the determination of bloodcomposition parameters is synchronised with the heartbeat withoutspecial means for pulse measurement.

Preferably, the characteristic changing in accordance with the heartbeatrhythm is selected to be proportional to oxygen content of the blood bydetermining a slope of the measured transmittance spectrum around 805nm, that slope changing substantially as a function of the oxygencontent of the blood. This spectrum slope can be determined for exampleon the basis of a difference of spectrum values measured at wavelengthsof 780 nm and 830 nm. The determination of blood composition parametersis advisably carried out on the basis of spectrum values taken at themoment of maximum oxygen content, and the spectrum values taken atconsecutive maximum oxygen content, or blood composition parametervalues determined on this basis, are averaged. However, it is notnecessary to carry out the determination of blood composition parametersalways on the basis on the spectrum values taken at the moment ofmaximum oxygen content. From the aspect of the invention the onlyimportant factor is that spectrum values measured in the same phase ofthe heartbeat period are used for determination.

In the case of a spectrum recording period of a much shorter time thanthe heartbeat period, measurements may follow one another without apause and the spectrum values measured during a period corresponding tothe heartbeat period or its integral multiple, or the blood compositionparameter values determined on this basis, are to be averaged.

On the other hand, the invention is an apparatus for rapid non-invasivedetermination of blood composition parameters, comprising optical meansfor irradiating a blood-containing body part of a live organism with anelectromagnetic radiation of near-infrared wavelength range, means formeasuring spectrum values of an electromagnetic radiation transmittedthrough and/or reflected by the body part and a data processing unit fordetermining one or more unknown values of blood composition parameterson the basis of the measured spectrum values. The invention ischaracterised in that said optical means for irradiating and said meansfor measuring spectrum values comprise a first optical arrangement formeasuring a transmittance spectrum of the body part in a firstwavelength range from 700 nm to a wavelength value between 1000 nm and1100 nm and a second optical arrangement for measuring a reflectanceand/or interactance spectrum of the body part in a second wavelengthrange from said wavelength value to 1800 nm, and said data processingunit comprises means for determining said one or more unknown values ofblood composition parameters on the basis of a single spectrumcomprising spectrum values of the transmittance spectrum and spectrumvalues of the reflectance and/or interactance spectrum.

In order to carry out determination, the apparatus must be calibratedpreviously for each blood composition parameter to be determined in perse known manner on the basis of spectrum measurements carried out onblood samples of known composition.

Preferably, both the first and the second optical arrangements areadapted to be located at the same section of the body part, practicallyat the distal phalanx of a finger. However, the first opticalarrangement may be adapted to be located at one section of the bodypart, e.g. at the distal phalanx, while the second optical arrangementat another section of the body part, e.g. at the middle phalanx.

In another embodiment of the apparatus according to the invention, thefirst optical arrangement comprises controllable means for generating anelectromagnetic radiation of a wavelength in the first wavelength rangeand a first detector sensing the radiation exiting from the body partand being sensitive in the first wavelength range, and the secondoptical arrangement comprises controllable means for generating anelectromagnetic radiation of a wavelength in the second wavelength rangeand a second detector sensing the radiation exiting from the body partand being sensitive in the second wavelength range.

However, it is also possible that the first and second opticalarrangements comprise a common infrared radiation source, a firstdetector selective in the first wavelength range for sensing theradiation exiting from the body parts as a result of transmission, and asecond detector selective in the second wavelength range for sensing theradiation exiting from the body part as a result of reflection and/orinteractance.

In a further embodiment of the apparatus according to the invention, thedata processing unit comprises means for determining a characteristicchanging in accordance with the heartbeat rhythm of the live organism onthe basis of at least a part of the measured spectrum values of thetransmittance spectrum and the reflectance and/or interactance spectrum,and means for selecting the spectrum values for determination of saidone or more unknown values of blood composition parameters synchronouslywith periodical changes of said characteristic. Preferably, the dataprocessing unit comprises means for determining a characteristicproportional to oxygen content of the blood.

The method and the apparatus of the invention are suitable for rapidnon-invasive determination of one or more blood composition parameters,as glucose, protein, albumin, creatinine, carbamide, cholesterol,triglyceride, cholinesterase, haemoglobin content of the blood. Theapparatus may be implemented as a single-purpose instrument fordetermining a single blood composition parameter e.g. glucose in theblood, but it could also be designed as a laboratory instrument servingfor a simultaneous determination of several blood compositionparameters.

BRIEF DESCRIPTION OF DRAWINGS

The invention will hereinafter be described on the basis of advantageousembodiments and implementations depicted in the drawings, where

FIG. 1 is a schematic side view of an optical arrangement applicable inthe apparatus according to the invention,

FIG. 2 is a schematic top view of the optical arrangement shown in FIG.1,

FIG. 3 is a schematic side view of another embodiment of the opticalarrangement applicable in the apparatus according to the invention,

FIG. 4 is a schematic optical layout and block diagram of an embodimentof the apparatus according to the invention,

FIG. 5 is a flow diagram illustrating an embodiment of the methodaccording to the invention, and

FIG. 6 is a flow diagram illustrating another embodiment of the methodaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, identical elements or elements of identical functionsare shown with the same reference signs.

FIGS. 1 and 2 show an example of an optical arrangement to irradiate afinger 9 with a distal phalanx 1 and a middle phalanx 2, said opticalarrangement being applicable in the apparatus according to theinvention. The distal phalanx 1 is irradiated, on the one hand, with amonochromatic infrared radiation of variable wavelength fortransmittance measurement by a transmission optical arrangement 17 in ashorter wavelength range, e.g. a wavelength range from 740 to 1060 nmand, on the other hand, with a monochromatic infrared radiation ofvariable wavelength for measurement of reflectance and/or interactanceby a reflection/interactance optical arrangement 18 in a longerwavelength range, e.g. a wavelength range from 1060 to 1800 nm. Themonochromatic radiation of shorter wavelength reaches the distal phalanx1 through a small diameter fibre optics 3, while the diffuse radiationpassing through it is guided by a larger diameter fibre optics 4 to adetector 5, which is for example sensitive in the wavelength range from740 to 1060 nm. The radiation of longer wavelength is guided by anothersmall diameter fibre optics 6 to a surface 1A of the distal phalanx 1,where the reflected diffuse radiation is collected by a larger diameterfibre optics 7, which guides it to another detector 8 sensitive in thewavelength range for example from 1060 to 1800 nm. In practice, in orderto avoid flux fluctuations and other disturbing effects, bothmeasurements are advantageously carried out in a two-way mode ofoperation. In this optical arrangement, the infrared radiation sourcesconnected to fibre optics 3 and 6 issue monochromatic beams associatedwith each wavelength, in a way separated in time. The generating of themonochromatic beam may be carried out for example by a wide-bandradiation source and by a changeable set of filters which generate themonochromatic infrared beam from this wide-range radiation, connected tothis radiation source.

FIG. 3 depicts another optical arrangement for irradiating the finger 9,applicable in the apparatus according to the invention. It is shown thatin this optical arrangement only one illuminating infrared radiationsource 19 is provided for the transmittance and reflectance/interactancemeasurements, and in this radiation source 19 the radiation generatingelement is a halogen incandescent lamp 10 with tungsten filament. Afilter 11 is used to screen visible light from the radiation of theincandescent lamp 10. Via lens 12 distal phalanx 1 of the finger 9 isirradiated with the radiation passing through the filter 11 and fallinginto the near-infrared wavelength range, and then the radiation passingthrough the finger 9 and reflected from its surface 1A is detected bydetector arrays 14 and 16, respectively, in a way that narrow-band wedgeinterference filters 13 and 15 are placed directly in front of thedetector arrays 14 and 16, respectively. The bypass wavelength of thefilters 13 and 15 increases continuously and linearly, for example thatof the filter 13 from 740 nm to 1060 nm and that of the filter 15 from1060 nm to 1800 nm, at a length which corresponds to active surfaces ofthe detector arrays 14 and 16. The radiation passing through the distalphalanx 1 is sensed by for example a silicon detector array 14 sensitivein the range of shorter wavelengths, while the radiation reflected bythe distal phalanx 1 is sensed for example by an InGaAsP detector array16 sensitive in the range of longer wavelengths. It can be seen that inthis embodiment the transmission optical arrangement 17A consists ofinfrared radiation source 19, interference filter 13 and detector array14, while the reflection/interactance optical arrangement 18A consistsof infrared radiation source 19, interference filter 15 and detectorarray 16. Practically, this embodiment may also be implemented in atwo-way design. In these optical arrangements, the detector arrays 14and 16 have as many outputs as the number of detectors applied, and theyare preferably read one after the other by a multiplexer.

FIG. 4 shows a block diagram of an embodiment of the apparatus accordingto the invention, in which optical arrangements 17 and 18 associatedwith the finger 9 are designed similarly to that of FIGS. 1 and 2, withthe difference that the transmission optical arrangement 17 is connectedto the distal phalanx 1, but the reflection/interactance opticalarrangement 18 to the middle phalanx 2. The signal coming from CPU 20via bus 21 and I/O unit 22 actuates LED drive 23 which supplies currentpulses to LED array 24. From the radiation of LEDs operating in arelatively wide wavelength range (50 to 100 nm), optical grating 25selects a narrow wavelength band and supplies it through mirror 26 andbeam splitter 27 on the one hand to fibre optics 3 which guidesradiation to the distal phalanx 1, and on the other hand to fibre optics28 which guides the radiation to a reference detector 29. Amplifier 30amplifies the output signal of the detector 29 and so it reaches througha multiplexer 31 an A/D converter 32, the output digital signal of whichgets to the CPU 20 via bus 21. The diffuse radiation passing throughphalanx 1 is guided by a large diameter fibre optics 4 to a measuringdetector 5, the output signal of which is amplified by an amplifier 33,and so it reaches the CPU 20 via multiplexer 31, A/D converter 32 andbus 21.

On the distal phalanx 1, transmittance is measured in the shorterwavelength range penetrating deeper (e.g. from 740 to 1060 nm), while onthe middle phalanx 2 reflectance/interactance is measured in a lesspenetrating wavelength range (e.g. from 1060 to 1800 nm). The method ofmeasurement on the middle phalanx 2 is similar to that of themeasurement carried out on the distal phalanx 1. The signal coming fromthe CPU 20 via bus 21 and I/O unit 34 actuates a LED drive 35 whichsupplies current pulses to a LED array 36. From the radiation of LEDsoperating in a relatively wide wavelength range (50 to 100 nm), opticalgrating 37 selects a narrow wavelength band and supplies this throughmirror 38 and beam splitter 39 on the one hand to fibre optics 6 whichguides the radiation to the middle phalanx 2, and on the other hand tofibre optics 40 which guides the radiation to a reference detector 41.The output signal of the detector 41 is amplified by amplifier 42, andso it reaches via multiplexer 43 an A/D converter 44, the output digitalsignal of which reaches CPU 20 via bus 21. The diffuse radiationreflected by phalanx 2 is guided by a large diameter fibre optics 7 tomeasuring detector 8, the output signal of which is amplified byamplifier 45, and so it reaches CPU 20 through multiplexer 43 and A/Dconverter 44, via bus 21.

The signals as well as the constants and coefficients of equationsdescribing the relationship between the signals and the bloodcomposition parameters/spectrum values to be determined are stored inRAM 46 and ROM 47 linked to bus 21. Display 49 is connected to bus 21via I/O unit 48 to display the results of measurement. CPU 20, bus 21,RAM 46, ROM 47, I/O unit 48 and display 49 make up a data processingunit 50, to which other peripherals may also be connected. In theembodiment shown, the data processing unit 50 generates the quotient andlogarithm of the signals from measuring detector 5 and referencedetector 29, and measuring detector 8 and reference detector 41,respectively, and this unit also compares the signal so obtained to astored standard signal, which latter may be obtained by carrying out themeasurement by replacing the finger 9 with a standard dummy finger. Forthis apparatus, it is sufficient to carry out the measurement with thedummy finger at relatively longer intervals, e.g. every week or once amonth, thereby updating the standard signal stored. By the standardsignal, the error stemming from slow changes of the apparatus can beeliminated.

The operation of the apparatus according to the invention can besynchronised with the heartbeat of the patient. This can be carried oute.g. by connecting a pulse detector 51 to the finger 9, and the outputsignal of this detector reaches CPU 20 through amplifier 52 and I/O unit53 via bus 21. Preferably, a temperature detector not shown in thedrawing may also be linked to the finger 9 and the output signal of thistemperature detector is similarly supplied to CPU 20 via anotheramplifier and I/O unit. By means of temperature measurement, errorsstemming from body temperature fluctuations can be compensated.

In FIG. 4, fibre optics 3, 4, 6 and 7 provide a flexible opportunity forguiding the radiation to the examined body part, in this example to thefinger 9, and for guiding the radiation away from the body part. Theiradvantage is that, on the one hand, they separate the electronic andoptical units from the body part to be measured and, on the other hand,by means of the application of appropriate springs they can be flexiblyadjusted to the surface to be measured and finally by increasing thebatch diameter, a larger flux from the diffuse radiation passing throughand reflected from the body part to be measured can be supplied tometering detectors 5 and 8, thereby improving the signal to noise ratio.The fibre optics 3, 4, 6 and 7, the pulse detector 51 and thetemperature detector, if any, are suitably located in a single probe,into which the person to be examined inserts his/her finger 9.

According to the invention, synchronisation with the heartbeat may alsobe carried out by determining a characteristic changing in accordancewith the heartbeat on the basis of measured spectrum values. Suchcharacteristic may be e.g. a spectrum value at a particular wavelengthor the slope of the spectrum around 805 nm, which slope changes as afunction of the oxygen content of the blood. The characteristic is to bedetermined from spectrum values measured with a frequency higher thanthe period of the heartbeat. In this case it is not necessary to usepulse detector 51, amplifier 52 and I/O unit 53. Advantageousembodiments of synchronisation on the basis of measured spectrum valuesare described with reference to flow diagrams shown as examples in FIGS.5 and 6.

In FIG. 5, after the starting step 60 (START), in step 61 the initialzero values of index p and blood composition parameter Q is adjusted,and in step 62 the adjustment of the initial zero value of index i andmarker L for controlling the programme takes place, where p is thesequence number of a detected maximum value of the oxygen content ofblood, and i is the sequence number of measured spectrum values. In step63, measurement and storing of spectrum values V₁, . . . V_(h), . . .V_(j), . . . V_(n) are carried out, where V_(h) and V_(j) are the twospectrum values, for example the spectrum values measured at wavelengths780 nm and 830 nm, on the basis of which the value of the oxygen contentchanging in accordance with the heartbeat is determined. In step 64,difference D_(i) of spectrum values V_(j) and V_(h) is generated, andthen in step 65 it is examined whether the value of index i is zero. Ifi=0, that is the very first measurement has been carried out, in step70, index i is incremented and the program returns to step 63. If i≠0,then in step 66 a difference M_(i) between the actual and previousvalues of difference D_(i) is generated. Next, in step 67 it is examinedwhether M_(i) ≦0 is valid. If not, then the actual value of D_(i) ishigher than the previous value of D_(i-1), that is the oxygen contenthas increased visa-vis the previous spectrum measurement and accordinglyin step 69, marker L will be adjusted to the value 1, and then in step70, index i is incremented and the programme returns to step 63. If theconditions of M_(i) ≦0 is satisfied, i.e. the oxygen content has notchanged or decreased, it is examined in step 68 whether the value ofmarker L is zero. If yes, no previous increase of oxygen content hasoccurred yet, and so in step 70, index i is incremented and theprogramme returns to step 63. If the value of marker L is not zero, i.e.it is 1, then the maximum value is involved or just passed, and so instep 71, index p is incremented, and then in step 72 the value of bloodcomposition parameter Q_(p) is calculated from the spectrum values lastmeasured and this is added to the so far obtained values of bloodcomposition parameter Q. Next, in step 73 it is examined whether thevalue of index p is lower than k, where k is the number of spectrummeasurements intended to be used for the average calculation. If p< k,the programme returns to step 62, and the cycle is repeated. If p=k,i.e. the blood composition parameter values calculated from k spectrummeasurements have been summarised, in step 74, the stored value of bloodcomposition parameter Q is divided by k, i.e. an average is generated.It can be seen that in generating the average the programme alwaysselects, that is takes into consideration, the result of the spectrummeasurement which just follows the maximum value of the blood oxygencontent, i.e. determining the blood composition parameter Q is alwaysperformed on the basis of spectrum values measured in an identical phaseof the heartbeat period.

FIG. 6 shows another possible embodiment of synchronisation on the basisof the maximum value of the oxygen content. In this case, an average ofa blood composition parameter is determined from all spectrum valuesmeasured between two maximum rates of the oxygen content. Only thoseparts of the flow diagram will be described which deviate from the flowdiagram shown in FIG. 5. After step 63, it is examined in step 75whether the value of index p is zero. If yes, i.e. the first oxygencontent peak has not been reached yet, the programme continues with step64. If no, i.e. the value of index p is 1, then in step 76 the value ofblood composition parameter Q_(i) associated with the spectrum valuesmeasured last is determined, and this is added to the values so farobtained for blood composition parameter Q and then the programmecontinues with step 64. If in step 68, the value of L is 1, then in step71 index p is incremented and then in step 77 it is examined whether thevalue of index p is 1. If yes, the programme returns to step 62 and ifnot, then in step 78 the stored value of blood composition parameter Qis divided by (i+1), i.e. an average of values of blood compositionparameters Q determined between two oxygen peaks is generated. It can beseen that the method as per FIG. 6 yields measuring results faster thanthat in FIG. 5, because it calculates the average from the results ofall spectrum measurements between two oxygen peaks. Of course, aparticular apparatus must be calibrated in accordance with the selecteddetermination method of the blood composition parameter Q.

According to the invention, transmittance spectrum values V_(t1),V_(t2), . . . V_(ta) of number a are measured at wavelength valuesλ_(t1), λ_(t2), . . . λ_(ta) and reflectance/interactance spectrumvalues V_(r1), V_(r2), . . . V_(rb) of number b are measured atwavelength values λ_(r1), λ_(r2), . . . λ_(rb). The two spectra arehandled as a single spectrum consisting of spectrum values V₁, V₂, . . .V_(n), of number n, where n =a+b. The blood composition parameter Qsought is determined, e.g. by the application of the already mentionedMLR method, on the basis of a linear equation

    Q=k.sub.0 +k.sub.1 V.sub.1 +k.sub.2 V.sub.2 + . . . +k.sub.n V.sub.n(1)

where k₀, k₁, . . . k_(n) are constants that can be determined bycalibration.

If the above mentioned PCR and PLSR methods are applied, respectively,the equation is formally similar, but the independent variables arelatent variables, each of which depends on all measured spectrum values.The composition parameter Q sought can be determined on the basis of anequation

    Q=c.sub.0 +c.sub.1 S.sub.1 (V.sub.1, V.sub.2, . . . V.sub.n)+c.sub.2 S.sub.2 (V.sub.1, V.sub.2, . . . V.sub.n)+ . . . +c.sub.m S.sub.m (V.sub.1, V.sub.2, . . . V.sub.n)                         (2)

where c₀, c₁, . . . c_(m) are constants, S₁, S₂, . . . S_(m) are latentvariables, V₁, V₂, . . . V_(n) are the measured spectrum values and m<n. Again, the constants c₀, c₁, . . . c_(m) may be determined bycalibration.

Consequently, in the apparatus according to the invention, two spectraare measured simultaneously or one immediately after the other in thenear-infrared wavelength range, one transmittance spectrum in the rangeof shorter wavelengths and one reflectance/interactance spectrum in therange of longer wavelengths. From these, according to the invention, theblood composition parameter sought, for example the glucose content, isdetermined by handling the two spectra as a single spectrum. Theapparatus is calibrated by using several blood samples of differentknown composition by any per se known method--e.g. by one of the abovementioned MLR, PCR and PLSR methods--i.e. the equation describing therelationship between the blood composition parameter and the spectrumvalues to be measured is determined for each sought blood compositionparameter Q₁, Q₂, . . . Q_(c), where c is the number of bloodcomposition parameters to be determined. In calibration, the recordingof the spectrum must be synchronised with the heartbeat just like in thecase of the subsequent measurement, and on the basis of the measuredspectrum values, the blood composition parameter sought must bedetermined by the same method. For example, by applying the MLR method,calibration means that on the basis of measurements on at least n+1different blood samples of known composition, constants k₀, k₁, . . .k_(n) in the equation (1) are determined by methods of mathematicalstatistics.

We claim:
 1. A method for rapid non-invasive determination of bloodcomposition parameters, comprising the steps of:irradiating ablood-containing body part of a live organism with an electromagneticradiation of near-infrared wavelength range; measuring a transmittancespectrum of the body part at several wavelengths in a first wavelengthrange from 700 nm to a wavelength value between 1000 nm to 1100 nm;measuring at least one of a reflectance and an interactance spectrum ofthe body part at several wavelengths in a second wavelength range fromsaid wavelength value to 1800 nm; and determining at least one unknownvalue of the blood composition parameters on the basis of a singlespectrum comprising spectrum values of said transmittance spectrum andspectrum values of said at least one of a reflectance and aninteractance spectrum, wherein said transmittance spectrum is measuredon the distal phalanx of a finger of an examined person and said atleast one of a reflectance and an interactance spectrum is measured onthe middle phalanx of the same finger.
 2. The method according to claim1, wherein both said transmittance spectrum and said at least one of areflectance and an interactance spectrum are measured at least at ninewavelengths.
 3. The method according to claim 1, wherein the spectrumvalues of said transmittance spectrum and the spectrum values of said atleast one of a reflectance and an interactance spectrum are measuredconsecutively in time.
 4. The method according to claim 1, wherein thespectrum values of said transmittance spectrum and the spectrum valuesof said at least one of a reflectance and an interactance spectrum aremeasured at least partially alternately in time.
 5. The method accordingto claim 1, wherein both said transmittance spectrum and said at leastone of a reflectance and an interactance spectrum are measuredsynchronously with the heartbeat of the live organism.
 6. The methodaccording to claim 1, wherein one of said at least one unknown value ofthe blood composition parameters is the glucose content of the blood. 7.A method for rapid-invasive determination of blood compositionparameters, comprising the steps of:irradiating a blood-containing bodypart of a live organism with an electromagnetic radiation ofnear-infrared wavelength range; measuring a transmittance spectrum ofthe body part at several wavelengths in a first wavelength range from700 nm to a wavelength value between 1000 nm to 1100 nm; measuring atleast one of a reflectance and an interactance spectrum of the body partat several wavelengths in a second wavelength range from said wavelengthvalue to 1800 nm; determining at least one unknown value of the bloodcomposition parameters on the basis of a single spectrum comprisingspectrum values of said transmittance spectrum and spectrum values ofsaid at least one of a reflectance and an interactance spectrum, whereinboth said transmittance spectrum and said at least one of a reflectanceand an interactance spectrum are measured synchronously with theheartbeat of the live organism; and measuring at least a part of thespectrum values of said transmittance spectrum and said at least one ofa reflectance and an interactance spectrum with a frequency higher thana heartbeat period of the live organism, determining therefrom acharacteristic changing in accordance with a heartbeat rhythm, andselecting the spectrum values for determination of said at least oneunknown value of the blood composition parameters synchronously withperiodical changes of said characteristic.
 8. The method according toclaim 7, wherein said characteristic is selected to be proportional toan oxygen content of the blood by determining a slope of saidtransmittance spectrum around 805 nm.
 9. The method according to claim7, wherein said spectrum values are selected from same phases ofconsecutive periods of said characteristic, and said at least oneunknown value of the blood composition parameters is determined on thebasis of average values of said spectrum values.
 10. The methodaccording to claim 7, wherein said spectrum values are selected within aperiod or its integral multiple of said characteristic, and said atleast one unknown value of the blood composition parameters isdetermined on the basis of average values of said spectrum values. 11.The method according to claim 7, wherein one of said at least oneunknown value of the blood composition parameters is the glucose contentof the blood.
 12. An optical apparatus for rapid non-invasivedetermination of blood composition parameters after irradiating ablood-containing body part of a live organism with an electromagneticradiation of near-infrared wavelength range, the apparatus comprising:afirst optical arrangement for measuring a transmittance spectrum of thebody part in a first wavelength range from 700 nm to a wavelength valuebetween 1000 nm and 1100 nm, wherein said first optical arrangement isadapted to be located at the distal phalanx of a finger; a secondoptical arrangement for measuring at least one of a reflectance and aninteractance spectrum of the body part in a second wavelength range fromsaid wavelength value to 1800 nm, wherein said second opticalarrangement is adapted to be located at the middle phalanx of the fingerat which the first optical arrangement is located when said firstoptical arrangement is in place; and a data processing unit includingmeans for determining at least one unknown value of the bloodcomposition parameters on the basis of a single spectrum comprisingspectrum values of said transmittance spectrum and spectrum values ofsaid at least one of a reflectance and an interactance spectrum.
 13. Theapparatus according to claim 12, wherein said first optical arrangementcomprises controllable means for generating an electromagnetic radiationof a wavelength in said first wavelength range and a first detectorsensing the radiation exiting from the body part and being sensitive insaid first wavelength range, and said second optical arrangementcomprises controllable means for generating an electromagnetic radiationof a wavelength in said second wavelength range and a second detectorsensing the radiation exiting from the body part and being sensitive insaid second wavelength range.
 14. The apparatus according to claim 12,wherein said first and second optical arrangements comprise a commoninfrared radiation source, a first detector selective in said firstwavelength range for sensing the radiation exiting from the body part asa result of transmission, and a second detector selective in said secondwavelength range for sensing the radiation exiting from the body part asa result of at least one of reflection and interactance.
 15. Anapparatus for rapid non-invasive determination of blood compositionparameters, comprising:a first optical arrangement for measuring atransmittance spectrum of the body part in a first wavelength range from700 nm to a wavelength value between 1000 nm and 1100 nm; a secondoptical arrangement for measuring at least one of a reflectance and aninteractance spectrum of the body part in a second wavelength range fromsaid wavelength value to 1800 nm; and a data processing unitincludingmeans for determining at least one unknown values of the bloodcomposition parameters on the basis of a single spectrum comprisingspectrum values of said transmittance spectrum and spectrum values ofsaid at least one of a reflectance and an interactance spectrum, meansfor determining a characteristic changing in accordance with theheartbeat rhythm of the live organism on the basis of at least a part ofthe spectrum values of said transmittance spectrum and said at least oneof a reflectance and an interactance spectrum, and means for selectingthe spectrum values for determination of said at least one unknown valueof the blood composition parameters synchronously with periodicalchanges of said characteristic.